Methods for optimizing the gate stack of charge trapping NVSM devices are also examined in this thesis. The performance of silicon-rich and stoichiometric nitride layers are compared, as well as multi-layer nitrides composed of a mixture of the two types. Stoichiometric silicon nitride (Si3N 4) is shown to improve retention in MANOS devices without sacrificing programming speed.16 Figure 2-4 A base voltage sweep charge pumping measurement for SONOS
NVSM with 45/65/18A ONO and W/L=50/0.8I¼m at 1MHz ............................................
....... 18 Figure 2-5 Variable frequency charge pumping result for SONOSanbsp;...